>>1959802>>1959844>I didn't know that was a thing,Rear derailleurs have a specification called "chain wrap capacity" which is the range of gearing a rear derailleur can handle (longer cage = higher chain wrap capacity). I don't know if retaillers normally list it for the derailleurs they sell, you could check their websites. QBP lists it but QBP's storefront is only viewable by dealers.
In anon's case, if he wants to run 52/34 and 11/30, he would calculate 52-34=18 and 30-11=19, then calculate 18+19=37, so he needs a rear derailleur with a chain wrap capacity of 37 or greater.
